The present invention relates to a semiconductor device and, more particularly, to a semiconductor device in which a contact plug is formed by a self-aligned contact process and a method of fabricating the semiconductor device.
As a degree of integration increases for a semiconductor device, a process margin has been gradually decreased. Accordingly, a self-aligned contact (SAC) process is mainly used to form a contact plug for connecting a drain and a bit line, and a source and a storage electrode. Also, to further increase the process margin during the SAC process, a landing plug contact (LPC) (i.e., a type of contact pad) is formed on a contact area.
Even though a dry etch method using a high etch selectivity ratio is used for the SAC process, it is still difficult to secure a sufficient etch selectivity ratio. Thus, to prevent SAC fail (i.e., a phenomenon where a gate structure or a bit line is etched when the contact hole is etched) a hard mask formed of a nitride layer is thickly deposited on the gate structure or the bit line. As a result, the aspect ratio of a semiconductor structure increases so that the process margin decreases accordingly. This could lead to manufacturing problems, for example, the contact hole is not formed open during the formation of a contact.